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So, the Dow Jones Industrial Average fell some 235 points on Thursday, and the CBOE Volatility Index (VIX) advanced. You might be wondering what that means, and whether you should hedge your unhedged stock portfolio.

As the kids say, chillax. Nothing has happened to suggest a rethinking of the market's current risk list, which includes rising bond yields, currency fluctuations, tapering of the Federal Reserve's bond-buying program, China, mixed retail sales, and sundry economic data.

If you are terrified that stocks will soon plummet lower yet again, buy some puts. If you enter a Google search for buying puts to hedge, you will find the hedging formula on CBOE.com. Dealers will happily sell expensive hedges to rattled investors acting after the fact. But, dear readers, many smart investors would counsel moving on—the time to buy defensive puts was earlier, when options volatility was low.

MasterCard's implied volatility—the essence of options prices—is near record lows, so investors can buy the calls without paying a greed premium. The trade plays on the fact that MasterCard's stock has advanced in reaction to the past six analyst days.

Most options traders ignore analyst meeting, but a recent Goldman Sachs study found that analyst-day meetings influence options volatility as much as earnings reports.

"Because of this, and the tendency for stocks to trade up on analyst days, we find buying calls ahead of analyst-day events has been profitable, and has generated an average return of 22% for seven-day trades, from five days before to one day after the analyst day," John Marshall and Katherine Fogertey, Goldman's derivatives strategists, wrote in a recent note. Trade returns omit transaction costs.

It is significant that Icahn used Twitter to communicate with the market, and then used mainstream media to elaborate on his Tweets about a stock buyback. Apple's stock would have rallied if Icahn had released his news through traditional media outlets, which is a time-tested way for Wall Street heavies to break big news. But it is unclear whether traditional media would have sparked a $25 stock rally on extraordinary volume. Apple's rally suggests that information travels faster via Twitter than through the traditional major media outlets that have long ruled the information highways.

Twitter may offer users something even more valuable than direct, instant interaction with a huge, global audience. It may let people believe they are digesting or dismissing news as if it was their own opinion, which savvy spin doctors says is the value of trade journals and second-tier publications. Media prestige does influence how readers digest information. No one says they read about Topic X in Trade Journal Z: They simply absorb or dismiss the information as their own. By contrast, readers might acknowledging they read Topic X in the Times or elsewhere; that prevents news from being assimilated as personal opinion.

One Tweet does not a trend make, but Twitter increasingly seems to combine the velocity of prestige media with the informational digestive traits of trade publications, and that is an incredibly powerful tool.